Canada Post says a second day of rotating strikes by its workers could cause delays in mail and parcel deliveries across the country.

The series of walkouts began yesterday, involving work stoppages in four cities — Victoria, Edmonton, Windsor, Ont., and Halifax — to back postal employees’ contract demands.

But the Canadian Union of Postal Workers turned up the heat today, moving the job action to Toronto, where nearly 9,000 of its members walked off the job a minute after midnight.

In a statement, Canada Post spokesman Jon Hamilton said the Crown corporation would make every effort to minimize the impact on its customers.

But he warned the Toronto walkout will have a significant impact on operations which could result in nationwide delivery delays because the city is a key processing hub.

CUPW, which represents 50,000 postal employees, says it needs Canada Post to address issues that have stemmed from the explosive growth of parcel deliveries, including health and safety concerns and precarious work.